After studying the kinetic properties of glucose diP synthetase we will look for regulatory properties of such metabolites as ATP, Pi, 2, 3-DPG, and PEP. We will establish tissue distribution and whether an E-P intermediate is involved - either with serine or histidine depending on whether it evolved from phosphoglucomutase or phosphoglycerate mutase, respectively. Further studies will depend on these findings. The question of whether mannose-1, 6-P2 is synthesized in red cells by a separate enzyme will be examined. We think so at present based on early DEAE runs. A related problem is the path of glucose diP breakdown. The synthetase has no phosphatase activity. Such enzymes were described in liver in 1966 (Hashimoto and Yorhikawa), both soluble and microsomal. Since brain shows a very high rate of GdiP breakdown in ischemia (Lowry, 1969), t 1/2 approximately 1 min, there must be a very active phosphatase in brain that is closely regulated. We will continue studies on regulation of PFK in intact red cells. By varying the fructose concentration of the cell we can vary the F6P concentration in the steady state and try to evaluate the effects of 2, 3-DPG, ADP, Pi, etc. on the shape of the PFK rate vs. F6P curve. We have evidence that activators move the curve left and make it less sigmoidal. BIBLIOGRAPHIC REFERENCES: 1. A. Rose, J. V. B. Warms, and D. P. Kosow. A specific enzyme for glucose-1 6-bisphosphate synthesis. J. Biol. Chem., 250, 3466 (1975).